This week, the ratings of six software stocks on Portfolio Grader are down. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

Workday, Inc. Class A’s (WDAY) rating falls to a D (“sell”) this week, down from C (“hold”) the week prior. Workday provides software-as-a-service solutions for managing global businesses, combining a lower cost of ownership with an innovative approach to business applications. WDAY also rates an F in Portfolio Grader’s specific subcategory of Equity. To get an in-depth look at WDAY, get Portfolio Grader’s complete analysis of WDAY stock.

This is a rough week for SRS Labs (SRSL). The company’s rating falls to D from the previous week’s C. SRS Labs develops and licenses audio and voice enhancement technologies. The stock gets F’s in Earnings Growth and Margin Growth. For more information, get Portfolio Grader’s complete analysis of SRSL stock.

Taomee Holdings Ltd. Sponsored ADR’s (TAOM) rating falls this week to an F (“strong sell”), down from last week’s D (“sell”). Taomee Holdings produces children’s entertainment. The stock receives F’s in Earnings Growth, Earnings Momentum and Earnings Revisions. Margin Growth and Sales Growth also get F’s. The stock has a trailing PE Ratio of 156.50. To get an in-depth look at TAOM, get Portfolio Grader’s complete analysis of TAOM stock.

Mavenir Systems, Inc. (MVNR) earns a D this week, falling from last week’s grade of C. The stock gets F’s in Earnings Revisions and Equity. For more information, get Portfolio Grader’s complete analysis of MVNR stock.

This week, Zix Corporation (ZIXI) drops from a C to a D rating. Zix provides secure, Internet-based applications in a Software-as-a-Service (SaaS) model. The stock gets F’s in Earnings Growth, Earnings Momentum and Earnings Surprise. Shares of the stock have been trading at an exceptionally rapid pace, up twofold from the week prior. The stock currently has a trailing PE Ratio of 67.10. To get an in-depth look at ZIXI, get Portfolio Grader’s complete analysis of ZIXI stock.

Digimarc Corporation (DMRC) experiences a ratings drop this week, going from last week’s C to a D. Digimarc provides media identification and management solutions to commercial entities and government customers in the United States and internationally. The stock gets F’s in Earnings Momentum, Earnings Revisions and Equity. Margin Growth and Sales Growth also get F’s. For more information, get Portfolio Grader’s complete analysis of DMRC stock.

Louis Navellier’s proprietary Portfolio Grader stock ranking system assesses roughly 5,000 companies every week based on a number of fundamental and quantitative measures. Stocks are given a letter grade based on their results — with A being “strong buy,” and F being “strong sell.” Explore the tool here.